Lambda Patterns

# Create a Lambda function aws lambda create-function \ --function-name my-function \ --runtime python3.12 \ --role arn:aws:iam::123456789012:role/lambda-role \ --handler app.handler \ --zip-file fileb://function.zip \ --memory-size 512 \ --timeout 30 \ --environment Variables="{DB_HOST=db.example.com,LOG_LEVEL=INFO}" # Update function code aws lambda update-function-code \ --function-name my-function \ --zip-file fileb://function.zip # Invoke function aws lambda invoke \ --function-name my-function \ --payload '{"key": "value"}' \ --cli-binary-format raw-in-base64-out \ response.json

# Publish a layer zip -r layer.zip python/ aws lambda publish-layer-version \ --layer-name my-dependencies \ --zip-file fileb://layer.zip \ --compatible-runtimes python3.12 python3.11 # Attach layer to function aws lambda update-function-configuration \ --function-name my-function \ --layers arn:aws:lambda:us-east-1:123456789012:layer:my-dependencies:3 # Layer directory structure # python/ # lib/ # python3.12/ # site-packages/ # requests/ # boto3/ # nodejs/ # node_modules/ # express/

# Attach Lambda to VPC aws lambda update-function-configuration \ --function-name my-function \ --vpc-config SubnetIds=subnet-abc123,subnet-def456,SecurityGroupIds=sg-789012 # Required IAM permissions for VPC # AWSLambdaVPCAccessExecutionRole managed policy, or: { "Effect": "Allow", "Action": [ "ec2:CreateNetworkInterface", "ec2:DescribeNetworkInterfaces", "ec2:DeleteNetworkInterface" ], "Resource": "*" } # Note: Lambda in VPC needs NAT Gateway for internet access # Avoid single-AZ subnet configs to prevent cold start spikes

# Provisioned Concurrency (pre-warmed instances) aws lambda put-provisioned-concurrency-config \ --function-name my-function \ --qualifier LIVE \ --provisioned-concurrent-executions 10 # Reserved Concurrency (limit max instances) aws lambda put-function-concurrency \ --function-name my-function \ --reserved-concurrent-executions 100 # Best practices for cold start reduction: # 1. Use smaller deployment packages (< 10 MB) # 2. Prefer compiled runtimes (Go, .NET) over interpreted # 3. Init DB connections outside handler function # 4. Use Lambda SnapStart for Java (JVM snapshots) # 5. Avoid loading unused dependencies

# template.yaml (AWS SAM) AWSTemplateFormatVersion: '2010-09-09' Transform: AWS::Serverless-2016-10-31 Globals: Function: Runtime: python3.12 Timeout: 30 MemorySize: 256 Environment: Variables: TABLE_NAME: !Ref DynamoTable Resources: ApiFunction: Type: AWS::Serverless::Function Properties: Handler: app.handler CodeUri: src/ Events: ApiEvent: Type: Api Properties: Path: /items Method: get Policies: - DynamoDBReadPolicy: TableName: !Ref DynamoTable DynamoTable: Type: AWS::DynamoDB::Table Properties: BillingMode: PAY_PER_REQUEST AttributeDefinitions: - AttributeName: id AttributeType: S KeySchema: - AttributeName: id KeyType: HASH # Deploy with SAM CLI # sam build && sam deploy --guided